Privet, Andrey!
I'm wondering on this occasion, if using structs in an C API is an
issue, how do system libraries do it, for instance int fstat(int fd,
struct stat *buf); where "struct stat" is a header-defined C struct as
well. The same mechanism should be applicable to HDF5 as well, if there
are problems?
Poka,
Werner
On 05.05.2014 13:35, Андрей Парамонов wrote:
Hello HDF5 developers!
HDF5 library exposes a number of functions which take parameters in
form of C struct (H5E_error2, H5G_info_t, H5FD_class_t etc). It means
that C structs are efficiently a part of binary interface. However,
such interface causes some problems:
1) C struct layout is not guaranteed to be binary compatible among C
compilers. Even more, the same compiler may produce binary
incompatible struct layouts depending on compiler flags.
2) Languages other than C, although often having a notion of
tuple/record/struct, rarely have the exact, binary-compatible
equivalent of C struct (given 1), it's clear why). For example, both
Delphi "record" and Delphi "packed record" are not guaranteed to be
binary compatible with public structs from official HDF5 library
release. It makes using advanced HDF5 features from non-C languages
harder.
It would be of great help if public HDF5 C structs were of some
documented, easy-to-support format, most preferably without field
alignment (Delphi "packed record"). Or maybe there is at least some
compiler flag to force no alignment for *public* structs (forcing no
alignment for all structs might be bad for performance, I presume)?
Best wishes,
Andrey Paramonov
--
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